document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=313615>Question 313615</A>: <I><SPAN STYLE=\"word-break: break-all;\"> If a ball is thrown vertically upward from a height of 5 ft, with an initial velocity of 96 ft/s, its height h after t seconds is given by h = -16t^2 + 96t + 5. How long does it take the ball to pass through a height of 120 ft on the way back down to the ground? \r<BR>\n" );
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document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #224224 by </B><A HREF=/tutors/aboutme.mpl?userid=Alan3354><B>Alan3354(69443)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=Alan3354><IMG SRC=http://www.algebra.com/images/aboutme-small.gif BORDER=0 alt=\"About Me\" VALIGN=MIDDLE></A>&nbsp;<IMG SRC=http://www.algebra.com/cgi-bin/show-face.mpl?user=Alan3354><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=224224\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> If a ball is thrown vertically upward from a height of 5 ft, with an initial velocity of 96 ft/s, its height h after t seconds is given by h = -16t^2 + 96t + 5. How long does it take the ball to pass through a height of 120 ft on the way back down to the ground?<BR>\n" );
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document.write( "h = -16t^2 + 96t + 5<BR>\n" );
document.write( "120 = -16t^2 + 96t + 5 solve for t<BR>\n" );
document.write( "-16t^2 + 96t + 5 = 120<BR>\n" );
document.write( "-16t^2 + 96t + -115 = 0<BR>\n" );
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document.write( " <TR><TD  ALIGN=MIDDLE>Solved by <A  rel=nofollow HREF=http://wiki.algebra.com/index.php/Tutoring_-_pluggable_solvers>pluggable</A> solver: <A  rel=nofollow HREF=solve_quadratic_equation.solver>SOLVE quadratic equation (work shown, graph etc)</A></TD></TR>\n" );
document.write( "<TR><TD  ALIGN=LEFT>Quadratic equation <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=ax%5E2%2Bbx%2Bc=0 ALIGN=MIDDLE  ALT=\"ax%5E2%2Bbx%2Bc=0\"   DISABLED_style= \"max-width:90%; height:auto;\" > (in our case <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=-16x%5E2%2B96x%2B-115+=+0 ALIGN=MIDDLE  ALT=\"-16x%5E2%2B96x%2B-115+=+0\"   DISABLED_style= \"max-width:90%; height:auto;\" >) has the following solutons:<BR>\n" );
document.write( "  <BR>\n" );
document.write( "  <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=x%5B12%5D+=+%28b%2B-sqrt%28+b%5E2-4ac+%29%29%2F2%5Ca ALIGN=MIDDLE  ALT=\"x%5B12%5D+=+%28b%2B-sqrt%28+b%5E2-4ac+%29%29%2F2%5Ca\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
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document.write( "  For these solutions to exist, the <U>discriminant</U> <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=b%5E2-4ac ALIGN=MIDDLE  ALT=\"b%5E2-4ac\"   DISABLED_style= \"max-width:90%; height:auto;\" > should not be a negative number.<BR>\n" );
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document.write( "  First, we need to compute the discriminant <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=b%5E2-4ac ALIGN=MIDDLE  ALT=\"b%5E2-4ac\"   DISABLED_style= \"max-width:90%; height:auto;\" >: <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=b%5E2-4ac=%2896%29%5E2-4%2A-16%2A-115=1856 ALIGN=MIDDLE  ALT=\"b%5E2-4ac=%2896%29%5E2-4%2A-16%2A-115=1856\"   DISABLED_style= \"max-width:90%; height:auto;\" >.<BR>\n" );
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document.write( "  Discriminant d=1856 is greater than zero. That means that there are two solutions: <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=+x%5B12%5D+=+%28-96%2B-sqrt%28+1856+%29%29%2F2%5Ca ALIGN=MIDDLE  ALT=\"+x%5B12%5D+=+%28-96%2B-sqrt%28+1856+%29%29%2F2%5Ca\"   DISABLED_style= \"max-width:90%; height:auto;\" >.<BR>\n" );
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document.write( "    <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=x%5B1%5D+=+%28-%2896%29%2Bsqrt%28+1856+%29%29%2F2%5C-16+=+1.65370879821637 ALIGN=MIDDLE  ALT=\"x%5B1%5D+=+%28-%2896%29%2Bsqrt%28+1856+%29%29%2F2%5C-16+=+1.65370879821637\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "    <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=x%5B2%5D+=+%28-%2896%29-sqrt%28+1856+%29%29%2F2%5C-16+=+4.34629120178363 ALIGN=MIDDLE  ALT=\"x%5B2%5D+=+%28-%2896%29-sqrt%28+1856+%29%29%2F2%5C-16+=+4.34629120178363\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
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document.write( "    Quadratic expression <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=-16x%5E2%2B96x%2B-115 ALIGN=MIDDLE  ALT=\"-16x%5E2%2B96x%2B-115\"   DISABLED_style= \"max-width:90%; height:auto;\" > can be factored:<BR>\n" );
document.write( "  <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=-16x%5E2%2B96x%2B-115+=+%28x-1.65370879821637%29%2A%28x-4.34629120178363%29 ALIGN=MIDDLE  ALT=\"-16x%5E2%2B96x%2B-115+=+%28x-1.65370879821637%29%2A%28x-4.34629120178363%29\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "  Again, the answer is: 1.65370879821637, 4.34629120178363.\n" );
document.write( "Here's your graph:<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=graph%28+500%2C+500%2C+-10%2C+10%2C+-20%2C+20%2C+-16%2Ax%5E2%2B96%2Ax%2B-115+%29 ALIGN=MIDDLE  ALT=\"graph%28+500%2C+500%2C+-10%2C+10%2C+-20%2C+20%2C+-16%2Ax%5E2%2B96%2Ax%2B-115+%29\"   DISABLED_style= \"max-width:90%; height:auto;\" ></TD></TR>\n" );
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document.write( "t = 1.65 seconds going up<BR>\n" );
document.write( "t = 4.346 seconds falling<BR>\n" );
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